Convenience closures or can lids for containers of juices and certain other products may have full panel pull out portions in the lids. A score line in the lid defines a relatively large removable panel portion to permit removal of the contents from the container. Some such juices and other products are packed under pressure, and it may be desirable to package additional products under pressure, especially in thin wall drawn and ironed aluminum cans. When convenience containers are packed under pressure, the pressure is released when rupture of the score line in the easy opening end is initiated by lifting a pull tab which is attached to the can end or closure. The force of the pressure against the product side of the closure may cause uncontrolled propagation of rupture of the score line. Such uncontrolled propagation of the score rupture is undesirable.
It is well known to provide a vent release for full panel pull out convenience closures to relieve the internal pressure in the container before initiation of rupture of the score line around the removable panel portion. Such vent releases are disclosed in U.S. Pat. No. 3,724,709 to Westphal and U.S. Pat. No. 4,043,479 to Khoury, among others. However, such vent releases are not foolproof in that the vent does not always open before initiation of rupture of the primary score.
An improved large panel pullout convenience closure for pressurized containers is needed which is virtually foolproof against uncontrolled rupture of the score line around the removable panel.